Armatures of the type mentioned here are known. They contain an armature winding and a ferromagnetic main body. The main body comprises axially extending grooves distributed around the circumference. The cross sections of these grooves can have various designs, and they are suited for accommodating electrical conductors of the armature winding. Armatures of this type often have an impermissibly high unbalance. As a result, their concentric-running properties are not satisfactory.